Embedding material for electrical heating units.



106. COMPOSITIONS,

COATING R PLASTIC.

umtrnnsmwm CrosswReierence O -Fr SAMUEL r. wILEun, 0E PITTSBURGH,PENNSYLVANIA, AssIeNoR, BY MESNE Assm A mENTs, To HELION ELECTRICCOMPANY, A CORPORATION OF NEW JERSEY.

E BEDDING MATERIAL FOR EnEcTEIcAL HEATING (Inn s;

- filed May 23, 1914.

This is a division of my application filed- November 13, 1911, SerialNo. 660,121, and relates to improvements in embedding material forheating units, and the object of my invention is to produce an embeddingmaterial in which the heating unit may be embedded, and which will serveto protect the heating unit against breakage or excessive oxidation, andwill also serve as a good distributing medium for the heat generatedbythe unit.

My invention while serving for an embedding material, is especiallyadapted as an embedding material for high resistance heating units,which because of their high resistance, likewise have a high temperaturewhen a'current is passed through them.

Another object of my invention is to produce an embedding material whichwhile of high electrical resistance is a good heat c0n ductor and can bereadily shaped around the heating unit to be embedded, and in fact canbe given any desired shape or configuration;

Still another object of my invention is to produce an embedding materialwhich is inexpensive, and while having the characteristics abovementioned, has such a co-efficient of expansion that it is not affectedsudden temperature changes, and will not .crack or disintegrate underrapid changes the particles will adhere and permit the shaping of themass.

The whole may be placed in a suitable mold or die and under sufiicient"ressure to hold it together firmly and to give 1 e desireii shape.Instead of shaping under pres- I I Specification of Letters Patent.

sure, the embedding material may be made? v I I Patented Jan. 19, 1915..No Drawing. Original application filed November 18, 1911, Serial No.660,121. Divided'anli this application plastic-and applied as a pasteover the fila mentor heating unit to serveas an embede ding material.The heating l unit is, of course, placed'in the mass so as to beembedded, and with its ends arranged for suitable'electric connection. TWhen shaped, the mass is baked at a low temperature, and then brought toa high temperature which forms it into a hard durable mass.

The embedding material, as stated, can be used with very high resistanceheating units, even though when heated they have a temperature of highincandescence, and I have used it on heating units running as high as1500 degrees C. when heated. The reason for this is that the embeddingmaterial is such a good conductor of heat that it carries away the heatfrom the unit so rapidly that the embedding material itself is notaffected.

Silicate of soda is a common binding material for analogouscompositions, and serves perfectly the purpose intended, but otherbinders may be used, such for instance, as gum arabic, or any of thesugar compounds.

I can vary the conductivity of the embedding material, and to render itless conductive, can mix with it any desired percentage of alumina,silica, or other poor electrical conductors at high temperature. This"does not affect the general efiiciency of the embedding material. Itwill be readily seen that the embedding material can be given sufiicientmass and suitable shape to adapt it In carrying out the invention, thebetter way is to first coat the heating unit with a fine grade ofcarborundum so as to make an air tight seal, and then cover the unit andits coating with the coarser material having better drying qualities.

It will be understood that a high resistance and consequently hightemperature heating unit, especially in filament form, is not adapted toa great many heating purposes, but by embedding the heating unit inmaterial of the kind stated, I get a substantially large body, that is,large in relation to the heating unit, which makes a good dis- Examin rtributer of heat at .a. lower. temperature than that of the actual unit,and further, a body ofsuch character as to beadapted to a wide varietyof uses.

It will also be noted that the embedding material which I use, whilereadily adapting itself to any necessary shaping, afiords an electricinsulationagainst ordinary commercial voltages.

1. A heating unit consisting of an electrical conductor and a coveringenveloping the active part of the conductor and containing siliconcarbid, silica and a binder consisting of a liqnid havingthecharacteristics of silicate of soda.

2. A heatunit consisting of an electrical conductor and a coveringenveloping the active part of the conductor, said covering consisting ofvcarbid, silica, silicate of soda and Water.

I 3. A heat -unit consisting of anelectrical conductor and a coveringenveloping the active part of the conductor, said covering consisting offinely dividedrrefractory earbid, silica, silicate of soda, and aliquid.

. 4. A heat unit consisting of a wound electrical conductor, and acovering of high electrical resistance'b'ut of high heat conductivity,said covering containing finely divided refractory carbid, silica, and abinder consisting of silicate of sodaand a liquid.

In testimony whereof I affix my signature in presence of two witnesses,

. SAMUEL P. WILBU'R. Witnesses:

Gno. J. TAYLOR, E. S. CLARK'sON.

Copies, of this'patent ina yje obtained for five cents each, byaddressing the Commissioner of Patents,

' Washington, D. C.

